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Re: [RFC] Avoid mutex starvation when optimistic spinning is disabled

From Davidlohr Bueso <dave@stgolabs.net>
Newsgroups linux.kernel
Subject Re: [RFC] Avoid mutex starvation when optimistic spinning is disabled
Date 2016-07-22 20:10 +0200
Message-ID <rXN3A-Qn-17@gated-at.bofh.it> (permalink)
References (4 earlier) <rWMsV-1T0-5@gated-at.bofh.it> <rWRCh-58W-3@gated-at.bofh.it> <rWZTc-21W-15@gated-at.bofh.it> <rXtex-4cZ-11@gated-at.bofh.it> <rXN3A-Qn-19@gated-at.bofh.it>
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On Fri, 22 Jul 2016, Waiman Long wrote:

>I think making mutex_trylock() fail maybe a bit too far. Do we really 
>have any real workload that cause starvation problem  because of that. 
>Code that does mutex_trylock() in a loop can certainly cause lock 
>starvation, but it is not how mutex_trylock() is supposed to be used. 
>We can't build in safeguard for all the possible abuses of the mutex 
>APIs.

True, and that's actually why I think that 'fixing' the !SPIN_ON_OWNER case
is a bit too far in the first place: most of the archs that will care about
this already have ARCH_SUPPORTS_ATOMIC_RMW. The extra code for dealing with
this is not worth it imo.

Thanks,
Davidlohr

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Thread

[RFC] locking/mutex: Fix starvation of sleeping waiters Imre Deak <imre.deak@intel.com> - 2016-07-18 18:20 +0200
  Re: [RFC] locking/mutex: Fix starvation of sleeping waiters Peter Zijlstra <peterz@infradead.org> - 2016-07-18 19:20 +0200
    Re: [RFC] locking/mutex: Fix starvation of sleeping waiters Jason Low <jason.low2@hpe.com> - 2016-07-18 19:50 +0200
      Re: [RFC] locking/mutex: Fix starvation of sleeping waiters Imre Deak <imre.deak@intel.com> - 2016-07-19 19:00 +0200
        Re: [RFC] locking/mutex: Fix starvation of sleeping waiters Jason Low <jason.low2@hpe.com> - 2016-07-20 01:10 +0200
        [RFC] Avoid mutex starvation when optimistic spinning is disabled Jason Low <jason.low2@hpe.com> - 2016-07-20 01:20 +0200
          Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Jason Low <jason.low2@hpe.com> - 2016-07-20 06:50 +0200
            Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Imre Deak <imre.deak@intel.com> - 2016-07-20 15:40 +0200
              Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Jason Low <jason.low2@hpe.com> - 2016-07-21 23:00 +0200
                Re: [RFC] Avoid mutex starvation when optimistic spinning is disabled Davidlohr Bueso <dave@stgolabs.net> - 2016-07-22 20:10 +0200
                Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Imre Deak <imre.deak@intel.com> - 2016-07-22 20:40 +0200
                Re: [RFC] Avoid mutex starvation when optimistic spinning is disabled Davidlohr Bueso <dave@stgolabs.net> - 2016-07-22 21:30 +0200
                Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Imre Deak <imre.deak@intel.com> - 2016-07-22 22:00 +0200
            Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Jason Low <jason.low2@hpe.com> - 2016-07-22 00:40 +0200
              Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Imre Deak <imre.deak@intel.com> - 2016-07-22 11:40 +0200
                Re: [RFC] Avoid mutex starvation when optimistic spinning is  disabled Jason Low <jason.low2@hpe.com> - 2016-07-22 20:50 +0200

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